This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-113696 filed on Apr. 14, 2000.
1. Field of the Invention
The present invention relates to a fuel pump sucking a fuel from a fuel tank and discharging suitable used for internal combustion engine.
2. Description of Related Art
JP-A-6-159282 discloses a fuel pump in which both axial ends of impeller blades incline, with respect to a partition wall, frontwardly in a rotating direction for smoothly introducing fuel into groove spaces formed between each of adjacent impeller blades.
JP-A-6-229388 discloses a fuel pump in which root side of impeller blades incline rearwardly in a rotating direction, and radial outer end of the blades incline frontwardly in the rotating direction. The object of JP-A-6-229388 is to give the fuel flowing out of groove spaces a kinetic energy for flowing frontwardly in the rotating direction, i.e., toward a fuel outlet, without wasting energy of the fuel flowing into the root of groove spaces.
However, in JP-A-6-159282, both axial ends of the blades incline with respect to the partition wall by the same angle from the root to the outer ends. Thus, the energy that the outer end of the blade gives to the fuel flowing out of the groove spaces is small, so that the flow speed of the fuel is insufficiently increased. In JP-A-6-229388, the front face of the impeller blade is formed in a flat in the rotating direction, the fuel hardly flows into the groove space. Thus, fuel amount flowing into the groove space is decreased, thereby reducing total energy given to the fuel. As described above, when fuel flow speed from the groove space is insufficient, or fuel amount flowing into the groove space is small, swirl speed of the fuel is reduced, thereby reducing pump efficiency.
An object of the present invention is to improve pump efficiency.
According to a first aspect of the present invention, the front face of a blade is formed in a concave shape with respect to a rotating frontward direction. The front face is inwardly concave from both axial ends of the blades, and warps from a root to a radial outer end of the blade to form the concave such that the concave gradually becomes small from the root to the radial outer end. Thus, fuel tends to flow into the root side of the front face, thereby increasing an amount of the fuel flowing into a groove space formed between adjacent blades. The concave of the front face becomes smaller as the radial outer end of the blade, so that the radial outer end of the blade gives the fuel large kinetic energy in the rotating direction from an impeller. Thus, flow speed of the fuel flowing out of the groove space is increased.
According to a second aspect of the present invention, a circumferential width of the groove space gradually decreases from the root to the radial outer end of the blade. Thus, flow speed of the fuel flowing out of the groove space is increased.